STEP 8 - WEATHER MAPS, FORECASTS, CATALOG SHEETS

Transcription

1 STEP 8 - WEATHER MAPS, FORECASTS, CATALOG SHEETS SailMail and WL2K users have two paths for retrieving weather information: copying synoptic weather maps, satellite pictures and printed information directly off the air via scheduled WEFAX broadcasts, or retrieving WEFAX from the Internet, WEFAX technology developed before WWII, is based upon the then state-of-the-art vacuum tube/photocell/ rotating-drum technology at the time. Still in use today, WEFAX is a relatively slow analog technology, susceptible to interference, noise. and signal fading. On the other hand it is relatively inexpensive to add WEFAX capability to an existing HF radio system. All that's required is a modest computer and some low-cost software. 8.1 Catalog Sheets What are they? The easiest way to download WEFAX documents through the SailMail and WL2K networks is by using Catalog Sheets. Catalog Sheets are listings of weather and Sailmail/WL2K related documents that can be fetched and downloaded to your PC as an . Weather forecasts downloaded using catalog sheets are identical to the forecast documents copied off-the-air using your HF radio. Speed and quality are the two main benefits for requesting WEFAX documents using Catalog Sheets as opposed to receiving them via WEFAX broadcasts. Downloading WEFAX documents is ten to twenty times faster than copying the same WEFAX off-the-air. Downloaded documents are retrieved digitally; therefore, they are an exact replica of the original. They do not suffer the image degradation from noise and signal fading typical of documents received via WEFAX broadcasts How to Request a Weather Document Access to the list of Catalog Sheets is through the Toolbar in the Message Index Screen. Click on WINDOW. CATALOGS, and then click on the + sign in front of Catalogs and the Saildocs Folder in Figure 4-1 above to open the document list in Figure 4-2 below.

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3 WL2K Network users have the added option of clicking on the + sign in front of the WL2K folder to access additional weather and WL2K-specific files and bulletins. To request a document click on the + sign in front of the relevant folder and place a check mark in the square in front of the document you want. You can request documents on a one time-only basis, or you can subscribe to them for a period of time. The example in Figure 4-3 two shows two selected documents: The Mid-Atlantic Offshore Forecast, and the Gulf of Mexico Offshore Forecast. The request for the Mid-Atlantic Offshore Forecast is a onetime request, and the network will deliver the forecast once. The request for the Gulf of Mexico Offshore Forecast however, is a subscription request. The system is being asked to have a copy of the Gulf of Mexico forecast available to download every day at 0600Z (UTC). Once subscribed to, a bulletin will continue to be delivered to your account until you cancel the subscription. To terminate a subscription go to the Catalog Sheets and request the subscribed-to document once. The next time you connect to the network your "once" request will be uploaded, changing your subscription to a onetime request. The next time you connect the network, the requested bulletin will be download for the last time (or until it's asked for again).

4 8.2 National Weather Service (NWS) FAX-Back (WL2K Only) The NWS provides a FAX-back service cruisers can use to retrieve weather documents. The system works by sending a command script to the NWS at ftpmail@ftpmail.nws.noaa.gov. The NWS FTP server executes the script, fetches the requested documents, and sends them to your WL2K mailbox. This example shown in Table 4-1 is asking the NWS WEFAX FTP server to fetch five different documents and send them to yourcall@winlink.org. The To: line contains the address of the NWS FTP FAX-Back server, the From: is your return address, and is where the requested documents will be sent, the Subject: line can contain anything you like, or be left blank, and the body of the message contains the executable script. The key to making the system work is to have an accurate listing of the file names for the NWS products, and to remember that the file names are case sensitive. The NWS produces an extensive list of weather products, with almost ninety documents covering the Pacific region, more than sixty covering the Atlantic region, and almost seventy covering the Gulf and Caribbean region. To request a copy of the latest product listing(s) for the area(s) of interest to you, send an to ftpmail@ftpmail.nws.noaa.gov following the format shown in Table 4.1 above. After the cd fax line type the weather products listing you need: get rfaxatl.txt for Atlantic area WEFAX products, get rfaxmex.txt for WEFAX products covering the Gulf and Southeastern Pacific region, and get rfaxpac.txt for WEFAX products covering the Northwestern Pacific These WEFAX listings are also available on the Internet as shown below.

5 1 2 3 Atlantic region WEFAX products broadcast by the USCG WEFAX station in Boston. { Mexico, the Caribbean, Tropical Atlantic and Tropical Pacific, broadcast by the USCG WEFAX station in New Orleans { Pacific products available from the USCG WEFAX station at Point Reyes (near San Francisco CA). { 8.3 Saildocs Ad hoc File Requests (WL2K Only) You can retrieve WEFAX documents directly from Saildocs.com without using the WL2K Catalog Sheets. Saildocs is an Internet-based service similar in nature to the NWS FAXback service, but much easier to use. Saildocs retrieves the same NWS WEFAX forecasts, maps, and satellite pictures that you get through the NWS FAX-back service without the cumbersome scripting. The advantages to requesting WEFAX documents through saildocs.com are: 1 2 Speed: Saildocs.com returns the requested files within in seconds, whereas the NWS FAX-Back service can take tens of minutes or longer. No finicky scripting: Simply send a request using plain English commands like send, subscribe (sub), unsubscribe (unsub).

6 To request a WEFAX document from Saildocs, address an to query@saildocs.com. Put anything you like in the Subject line, and in the body of the put your request. A request to Saildocs for the same documents requested in Table 4-1 of the NWS FAX-back section, is shown in Table 4-2 above. The request format is simple and easy to understand - it's simply the command send followed by a space and then the document file name. The documents returned in response to your request are the identical NWS documents returned by the NWS FAX-Back system. If you have a repeated need for a specific document(s), instead of using the one-time command send, you can subscribe to the document, and set the intervals when the documents will be fetched. For details on this and other features of saildocs.com send an to query@saildocs.com and in the body of the type "send help", and on the next line "send info" GRIB Files (Works with both Sailmail & WL2K) Both the SailMail and WL2K systems support Girded Binary (GRIB) wind prediction files. GRIB file information is based upon the NOAA GFS/AVN global computer model, not actual reported conditions. The GRIB wind prediction data predicts general wind flow, and is a useful tool when used in conjunction with other weather forecasting and analysis tools, but it should not be used as a standalone predictor. It's important to keep in mind that these GRIB data files are not reviewed by meteorologists and they do not allow for frontal, tropical, near-shore, geographical, or other local effects. As with most other SailMail and WL2K activities, requesting a GRIB file is accomplished from the Message Index Screen. Clicking on icon in the toolbar or selecting WINDOW,CATALOGS, brings up the Catalog Tree screen shown in Figure 4-4, Click on the plus sign in front of saildocs, then on the folder icon in front of grib FILES, to open a world map.

7 To select an area for which you want GRIB data, click on the icon to turn your cursor into a hand. Place the hand onto the map and while depressing the left mouse button position the map so that the area of interest is in view. Use the magnify tools as needed to enlarge the area of interest. When you're finished positioning the map, if you're interested in GRIB data for an area click on the and place the cursor at one corner of the desired area. While holding down the left mouse button draw the marquee diagonally across the map to the opposing boundary of the area of interest, dragging the marquee (blue square) to select the area for which you wish to receive GRIB data. If this is a one-time request, click the radio button in front of Request (to be sent once), or the Subscribe radio button if you wish to receive this data for a period of time, and then click the Request button. Airmail will format a request for these GRIB data and place the request into your Outbox. When you next connect to the SailMail or WL2K networks, your request will be automatically sent to query@saildocs.com. If vou want text data far a specific location, click on the spot forecast button, move the spot forecast button to the desired location on the map, and click the request button. Figure 4-5 shows a marquee selecting GRIB data for Florida and the Caribbean, and the "wind feather" map returned in response to the marquee-generated request.

8 Figure 4-6 below shows the text information returned for a "spot forecast". For a comprehensive discussion about GRIB ''Spot Forecast" send a blank to {spotforecasts@saildocs.com}.

9 8.4 GETFAX - Receiving Weather Map Broadcasts (WEFAX) The program GETFAX and its companion viewer and online weather data retrieving program ViewFAX are applets that turn your computer/hf radio /PTC-ll modem system into a high-quality Weather FAX (WEFAX) receiver. Beginning with Airmail V 3.4.xx GetFAX is integrated into Airmail, and can be accessed through the Modules Dropdown Menu or the rightmost icon on the Message Index Toolbar. Here are the steps for running GETFAX from within Airmail: Start GetFAX Make certain that the Airmail Terminal Screen is closed. Both GetFAX & the Airmail Terminal program use the same Com Port to communicate with your modem. If the Terminal Screen is running when you start GetFAX, GetFAX will be unable to access the modem's Com Port, you'll get a COM Port conflict error message, and GetFAX won't work. To start GetFAX double click on the GetFAX Icon located on the Airmail Message lndex Screen toolbar shown in Figure Initiate FAX Mode In the GetFAX Toolbar. Figure 4-8, select MODE, FAX, GeTFAX switch your modem to the FAX mode and activate the two adjacent drop-down menu windows. From the leftmost dropdown menu window click on the down arrow and choose the weather station from which you wish to receive a FAX, and from the adjacent dropdown menu window select a frequency.

10 Your PTC-ll/PTC-IIPro, or PTC-llusb will automatically tune your radio to the appropriate receive frequency. It the station is transmitting a FAX; you will see a signal waveform in the FAX Scope window located below the toolbar, and hear "FAX tones" on your radio. To begin receiving the weather FAX either click on the green button on the lower right side of the screen, or go the toolbar and select MODE, START. If you are using a PTC-lle/PTC-llex and your radio is not tuned by your computer, subtract 1. 9 khz from the number shown in the frequency dropdown window, and tune your radio to the resultant frequency. For example, if the frequency shown is khz. tune the radio to khz. To begin receiving a weather FAX, go back to the GetFAX Toolbar and select MODE, START, or click on the green start button.getfax will continue to receive Fax's as they are sent, filing each received FAX by date and time in the FAXFILES folder located under PROGRAM FILES. AIRMAIL. Weather FAX broadcasts are public broadcasts similar to AM or FM radio. They are totally separate from the Sailmail and WL2K networks, and have no impact on the amount of daily "connect" time you use. Receiving WEFAX broadcasts is a passive activity in that no information is transmitted by your station, and the power drain on your batteries is limited to the 1-2 amps it takes to operate your radio in the receive mode. 8.5 VIEWFAX Retrieving and Viewing GRIB and Other Weather Flies ViewFAX has two jobs; retrieve weather documents via the Internet, and display GRIB and WEFAX files stored in the Faxfilies subfolder. If you have an Internet connection ViewFax will almost instantly fetch any GRIB file or document listed on the Catalog Sheets. When you're connected to the Internet SailDocs fetches the requested document and delivers it to you within seconds. There's no waiting! There are several ways to open and view stored WEFAX files. One way is to start ViewFAX by double-clicking on the ViewFAX Desktop Icon, then from the ViewFAX toolbar click on FILE,OPEN. Then select any of the files listed as in Figure 4-9.

11 Another way to start ViewFAX is; 1 Start the Airmail program. 2 Open the Folder Tree by clicking on the leftmost icon in the Airmail toolbar 3 Navigate to the Faxfiles folder 4 Double-click on Faxfiles folder to open it. 5 Double-click on the file you want to view Retrieving Files Listed on Catalog Sheets To retrieve files from the Catalog List start ViewFAX by double-clicking on the ViewFAX icon. If all you see when ViewFAX starts running is the ViewFAX toolbar like the one on Figure 4-10 and a gray area beneath it, click on FILE/GET DATA. Next click on the + sign in front of Catalogs and Saildocs.Select any of the documents listed in the folder tree, or select GRIB and draw a marquee that captures your geographical area of interest.

12 8.6 WEFAX File Size and Pactor-III (P-III) WEFAX files are relatively large, averaging about 35KB in size, if you are proactively requesting and downloading WEFAX files from the NWS over the WL2K network, you need to be running Pactor-III. WEFAX files are large relative to the throughput speed of HF-based , and the 4x speed increase of P-III reduces what may take 12 minutes or so to download with pactor II to three minutes or so running pactor III, conserving both time and battery power.